The sampling of air within the air handling system of a structure is essential to the early detection of air quality dangers such as smoke or carbon monoxide. A conventional scheme for air sampling includes a housing containing a duct air quality detector such as a smoke detector, carbon monoxide detector or other types of air quality detectors such as particulate, humidity, or oxygen. A conventional duct detector housing is exposed to air from an air handling system by way of a sampling tube extending into a duct of the air handling system. The duct detector housing includes an exhaust port so as to create air flow through the detector housing. The housing exhaust port is often coupled to the duct being sampled so as to create a return flow of the sampled air back into the air handling system. Conventionally, an air handling tube is custom formed to accommodate duct dimensions relative to the housing. The tube is formed from an extended length of periodically perforated tubing. FIG. 1 depicts a conventional prior art duct detector housing equipped with conventional air sampling tubes and coupled to an air handling system duct.
Conventional air sampling tubes of a needed length are cut from periodically perforated tubing having a length greater than any that is anticipated to be used. This approach is not only wasteful of tubing material, but also requires field work to cut the tubing, and presents logistical problems associated with the transport and handling of tubing having a length of, for example, 5 feet. Alternatively, conventional air sampling tube construction has involved joinder of rotationally a specific sections of pre-apertured tubing as detailed in, for example, prior art FIG. 1. Regardless of construction, periodically perforated tubing is prone to hole fouling associated with particulate in the air handling system and in the instance of galvanized steel tubing the hole formation compromises coating protective integrity. The custom nature of assembly of an air sampling tube poses a problem of assuring proper hole directionality about a tube axis. This rotational symmetry increases both installation and inspection effort.
Thus, there exists a need for an air sampling tube having a tubular section that is only joined to another component in a unique orientation relative to an aperture in the tubular section. There further exists a need for an air sampling tube that has a tubular extension with an axially extending groove defined by edges where at least one of the edges is enveloped to form an eddy channel adjacent to the groove. Still further, there exists a need for an assembler or inspector to be able to identify the axial position of air intake holes on a tubular section without resort to movement of the air sampling tube.